Asif Ali Zardari, Pakistan's embattled president, will remain in hospital in Dubai until further notice after suffering a minor heart attack and undergoing an operation, officials said.

"The president went to Dubai following symptoms related to his pre-existing heart condition," Prime Minister Yusuf Raza Gilani's media office said in a statement on Wednesday.

"The president will remain under observation and return to resume his normal functions as advised by the doctors."

The 56-year-old head of state flew to the United Arab Emirates on Tuesday after falling ill in the midst of a major scandal over alleged attempts by a close aide to seek US help to limit the power of Pakistan's military.

His illness sparked media reports that he was contemplating resignation, but loyalists have ruled out any question that he may step down and the president has defied many critics in already holding onto power for three years.

Mustafa Khokhar, adviser to the prime minister, shot down claims that the president was planning to retire - saying "there's no question of any resignation".

Resignation calls

Although Zardari has survived numerous crises and calls for his resignation, he has come under increasing pressure from Pakistan's powerful military for allegedly seeking US help to curb its power.

The row centres on a memo sent in May to the US's then-chairman of the Joint Chiefs of Staff, Admiral Mike Mullen, seeking help over fears of a military coup following the US raid that killed Osama bin Laden.

Mansoor Ijaz, a Pakistani-American businessman, accused Haqqani of crafting the memo with Zardari's support. Haqqani has denied involvement and investigators have yet to prove to what extent Zardari may have been involved.

Haqqani was forced to resign as ambassador to Washington last month and Zardari said on Sunday that he would soon address a joint session of parliament.

It was not clear if the health scare would delay that plan.

The night raid by US special forces in a Pakistani garrison town on May 2 provoked outrage in Islamabad and humiliated the military, which was not informed of the operation beforehand.

Relations between the military and Zardari are understood to be tense.

Haqqani's departure was seen as forced by the army, and the political pressure on Zardari is mounting ahead of elections expected as early as next autumn.